Re: SIMD vs no SIMD on i686 (was: [Bug 3975] executable stack flag prevents use of libx264.so.148 with selinux in enforcing mode)

dominik(a)greysector.net wrote: There is an expectation that Fedora packages run on any CPU supported by Fedora. For i686, that is currently any i686 CPU with cmov. You are not allowed to assume ANY vector instructions, not SSE2, not SSE (1), not even MMX. (It is of course fine to use all of these with appropriate runtime detection.) I think it is very reasonable to expect the same from RPM Fusion packages, considering that RPM Fusion's policy is normally to follow Fedora policies except for licensing stuff and kernel modules. This is all the more true for a library package, where the library can end up being used in many applications. Those applications will not necessarily want to encode H.264 in real-time, it can be perfectly acceptable for something like the ffmpeg command line to take longer than the video's playing length to encode it. So for those stuck with such an old machine, it is better to have a library that works (slowly) than one that just crashes with a SIGILL (illegal instruction). I know some upstreams are uncooperative at this. Aggressive reverts of offending upstream patches are one solution, changing #ifdefs from something like: #ifdef __i686__ to something like: #if defined(__i686__) && defined(__SSE2__) are another. I did a combination of both to fix QtWebEngine: http://pkgs.fedoraproject.org/cgit/rpms/qt5-qtwebengine.git/tree/qtwebeng... (The Chromium packaging should also use such a patch, but currently doesn't. Send your complaints about that to spot. :-) ) Kevin Kofler